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For the 100 Mbps EFM fiber optic links (100BASE-LX10 and
100BASE-BX10)
we specified a BER requirement of 1E-12, consistent with
the BER requirement
for gigabit links. We recognized that this would be
impractical to test in a
production environment, so we defined a means to
extrapolate a BER of 1E-12
by testing to a BER of 1E-10 with an additional 1 dB of
attenuation. See
58.3.2 and 58.4.2.
Howard Frazier
Broadcom Corporation From: Roger Merel [mailto:roger@LUXTERA.COM] Sent: Monday, August 28, 2006 1:54 PM To: STDS-802-3-HSSG@listserv.ieee.org Subject: Re: [HSSG] BER Objective David, Prior to 10G, the BER standard (for optical
communications) was set at 1E-10 (155M-2.5G). At 10G, the BER standard was
revised to 1E-12. For unamplified links, the difference between 1E-12 and
1E-15 is only a difference of 1dB in power delivered to the PD. However,
the larger issue is one of margin and testability (as the duration required to
reliably verify 1E-15 for 10G is impractical as a factory test on every unit)
especially since we’d want to spec worst case product distribution at worst case
path loss (cable+connector loss) and at EOL with margin. Thus in reality,
all products ship at BOL from the factory with a BER of 1E-15 and in fact nearly
all will continue to deliver 1E-15 for their entire life under their actual
operating conditions and with their actual cable
losses. Thus, if by “design target”, you mean a
worst case-worst case with margin to be assured at EOL on every factory unit,
then this is overkill. I might be willing to entertain a 1E-13 BER as this
would imply that same number of errors per second (on an absolute basis;
irrespective of the number of bits being passed; this takes the same time in the
factory as verifying 1E-12 at 10G although this is in fact a real cost burden
which adversely product economics); however, this would not substantially change
the reality of the link budget. It would make for a sensible policy for
the continued future of bit error rate specs (should their be future
“Still-Higher-Speed” SG’s). -Roger From: Martin,
David (CAR:Q840) During the discussion on Reach
Objectives there didn’t appear to be any mention of corresponding BER.
Recall the comments from the floor
during the July meeting CFI, regarding how 10GigE has been used more as
infrastructure rather than as typical end user NICs. And that the application
expectation for 100GigE would be similar. Based on that view, I’d suggest a
BER design target of (at least) 1E-15. That has been the defacto expectation
from most carriers since the introduction of OC-192 systems.
The need for strong FEC (e.g., G.709
RS), lighter FEC (e.g., BCH-3), or none at all would then depend on various
factors, like the optical technology chosen for each of the target link lengths.
...Dave David W. Martin |